Field of the Invention
The present invention is directed to a method and apparatus for cutting and stripping optical fibers.
Discussion of the Known Art
When manufacturing a high power cladding pumped fiber laser, a length of a polymer coating on the fiber is cut and stripped from one end of the fiber, and the stripped end is recoated. When the fiber operates as a laser, substantial optical power is pumped through the fiber cladding and interacts with the coating. Therefore, when the coating is stripped off the end of the fiber, the edge of the coating that remains on the fiber and the underlying cladding must be smooth and clean to keep the operating temperature of the fiber laser relatively low. Defects at an edge of the coating or the recoating, or any particles present on the surface of the fiber cladding, will induce heating and cause the fiber laser to fail.
While it is possible to use a liquid or acid to remove the coating (see, e.g., U.S. Pat. No. 5,298,105 (Mar. 29, 1994)), acid stripping can raise reliability issues over the long term. Therefore, mechanical tools are typically used for cutting and stripping coated or jacketed optical fibers. Such tools are commercially available from, inter alia, Jonard Tools, Tuckahoe, N.Y. 10707, and Micro Electronics, Inc., Seekonk, Mass. 02771. See also U.S. Pat. No. Re. 30,342 (Jul. 22, 1980), U.S. Pat. No. 4,271,729 (Jun. 9, 1981), and U.S. Pat. No. 6,643,448 (Nov. 4, 2003), and Pub. No. US 2014/0338195 (Nov. 20, 2014), all of which are incorporated by reference.
As mentioned, after the coating is stripped from the end of the fiber, the edge of the coating left on the fiber must be clean and smooth so the fiber can operate as a laser at high power without overheating. If a mechanical tool is used and the tool blades are not sufficiently sharp, the coating will be crushed rather than cleanly sliced, and regions will be produced where the coating separates or delaminates from the fiber cladding.
FIG. 1 is a microscope image of an end of a coated fiber 10, showing a delamination region at a cut edge 18 of the coating 12 after a length of the coating was cut and stripped from the end of the fiber by a conventional tool, leaving a stripped region 14. After the fiber 10 is spliced to another optical fiber or otherwise processed, the stripped region 14 is typically recoated with a low index polymer. During operation of the fiber 10 as a laser, pump light from a multi-mode optical diode laser or other source is guided by a boundary 16 between the cladding 14 and the coating 12 on the fiber 10. Therefore, any delamination or tear at the cut edge 18 of the coating will disturb the properties of the boundary 16 and cause the fiber 10 to overheat during laser operation.
Tools that use ruby or diamond blades to cleave an optical fiber to obtain a mirror flat surface on a terminating end of the fiber, are commercially available from, inter alia, Thorlabs Inc., Newton, N.J. 07860 and Delaware Diamond Knives, Wilmington, Del. 19805. See also U.S. Pat. No. 4,621,754 (Nov. 11, 1986) which is incorporated by reference. Notwithstanding, a need exists for a method and apparatus for cutting and stripping a coating from an end of an optical fiber so that the coating remaining on the fiber is free of tears or delamination.